Altoona to Homestead

The former Rock Island main line from Blue Island (Chicago) to Council Bluffs is now operated, and mostly owned, by the Iowa Interstate railroad. Once double track, current-of-traffic, Automatic Block Signals, the line is now single track, Track Warrant Control, unsignaled (dark territory), maximum speed 49 mph.

The Third sub. begins at Newton (MP 322.5), where an erstwhile Rock Island branch once trailed in from the south, an erstwhile C&NW line once came in on the north side,  and an erstwhile Minneapolis & St. Louis branch once left to the southeast, and there is a wooden depot to the north, with a park to the south, and heads northeast, past two grade crossings, a dirt road grade crossing, three grade crossings, a spur trailing in on the south side, three yard tracks on the north side Newton Yard (MP 320.0), three tracks from silos on the north side, four tracks, two-track mechanical shop, with tracks joining to become three tracks adjacent to the main, and yard tracks on the south side, a grade crossing, and two dirt road grade crossings.

The line turns curvily east-southeast, past two dirt road grade crossings, a bridge over a river, a grade crossing, spur to feed silos on the south side, the 3,955 ft. siding at Kellogg (MP 313.8), a grade crossing, a dirt road joins alongside to the north, a road bridge overhead, a bridge over a stream, a detector at MP 307.9, and a bridge over a dirt road, curvily northeast, past Turner, and a spindly road bridge overhead, east-southeast, past an angled grade crossing, five grade crossings in town, a street alongside to the south, a grade crossing, a depot on the north side and the flat crossing with the UP (former Minneapolis & St. Louis, later C&NW) at Grinnell (MP 302.7), a grade crossing, a grade crossing at East Street, the siding on the south side at Grinnell, and a grade crossing.

There are five dirt road grade crossings, silos to the north at the erstwhile Rock Island siding at Ascalon (MP 297.3), a grade crossing, a dirt track grade crossing, a dirt road grade crossing next to a road bridge over a stream, a grade crossing in Malcolm (MP 293.7), a turn east-northeast, silos on the north side, a road bridge overhead at the 7,835 ft. siding at Brooklyn (MP 287.7), and a dirt road grade crossing, and east, past a siding on the south side at Carnforth (MP 282.5), where an erstwhile C&NW line once crossed, a detector at MP 282.9, a dirt road grade crossing, a dirt track grade crossing, and Victor (MP 279.9).

The line turns east-northeast, past a bridge over a stream, a dirt road grade crossing, a grade crossing in Ladora (MP 273.9), a dirt road grade crossing, three dirt track grade crossings, a dirt road grade crossing, a road alongside to the south, a bridge over a river, and a grade crossing at the west end of the 5,330 ft. siding at Marengo (MP 267.3), and just south of due east, past silos on the north side, a grade crossing still in town, sewage ponds to the south, a dirt track grade crossing, US 6 approaching on the south side, a dirt road grade crossing, a bridge over a stream, a dirt track grade crossing, a pond to the north, three dirt track grade crossings, a grade crossing, a dirt track grade crossing, a dirt road grade crossing, a new yard being built (in June, 2012, opened October 29, 2012) on the south side, with three tracks, then five tracks and seven tracks, and a new mechanical shop on the south side, with three tracks to it, all at South Amana (MP 262.1), followed closely by the west apex of the wye at Yocum Connection (MP 259.0), where the IAIS connects with the CRANDIC Third sub. and the erstwhile Milwaukee Road line once trailed in on the south side before crossing over to become what is now the CRANDIC.